Shelf



FIG. 1 is a top, front, and right side perspective view of a shelfshowing my new design;

FIG. 2 is an enlarged front elevational view thereof;

FIG. 3 is an enlarged rear elevational view thereof;

FIG. 4 is an enlarged right side elevational view thereof; the left sidebeing a mirror image of that shown;

FIG. 5 is an enlarged top plan view thereof; and,

FIG. 6 is an enlarged bottom plan view thereof.

The ornamental design for a shelf, as shown and described.